Recently, there has been increased awareness and concern for environmental protection from radioactive contaminants produced by humans. There is a need for appropriate monitoring devices that are capable of monitoring selected contaminants, which have detectable limits below typical prior art monitoring levels. Such devices and their methods of operation should be simple and low in cost. The methods of the invention are directed to uranium enrichment measurement in liquids and 10 nanocuries per gram (nCi/g) assay for bulk solid transuranic wastes, a monitoring level not achieved by prior art devices.
According to the recently released AEC Manual Chapter 0511 (Radioactive Waste Management), transuranium contaminated solid wastes are "those contaminated with certan alpha-emitting radionuclides of long halflife and high specific radiotoxicity to greater than 10 nanocuries/gram . . . ". The radionuclides included are plutonium and transplutonium nuclides except .sup.238 Pu, and .sup.233 U and its daughter products. The 10-nCi/g level is a criterion for choosing different means of handling different activity levels of transuranium-contaminated solid wastes. Accordingly, a monitoring scheme is needed for measurements at and below this activity level. But due to the very low natural radiation yields (spontaneous fission neutrons and high-energy gamma rays) at such activity levels a different approach than the more conventional assay systems is needed.